Reye's syndrome (R.S.) is an illness of childhood in which mitochondrial injury, particularly in liver, has been suggested to be of central importance. Aprille reported that concentrates of R.S. serum stimulate respiration and uncouple oxidative phosphorylation beyond Site I and II of electron transport in isolated rat liver mitochondria. This has partially been confirmed by Ansevin and by ongoing work in our laboratory. These observations suggest that there may be a serum factor in R.S. serum affecting respiration and thus providing support for the concept that R.S. is a disorder of mitochondria. However, there is disagreement at the present time about the nature and site of action on the "serum factor". Clinical information suggests that fatty acid and pyruvate metabolism are significantly disturbed in patients with R.S. Effects of R.S. serum on fatty acid and pyruvate metabolism have as yet not been studied. The present proposal is designed to further characterize Aprille's findings on respiration polarographically with compounds that enter site III of electron transport. In addition, I will determine by measuring ATP directly if oxidative phosphorylation is truly uncoupled, and evaluate the presence of potential uncouplers of oxidative phosphorylation--i.e. free fatty acids and calcium in R.S. serum. Mitochondrial fractions will be examined to determine whether Aprille's findings are related to increased transport of substrates for respiration. Intact mitochondria will be incubated with 14C labelled palmitate to assess fatty acid oxidation in the presence of R.S. serum. Other tissues will be examined and the possibility of using cultured whole cells (hepatocytes or fibroblasts) explored so as to consider the integration of glycolysis and mitochondrial functions in vitro.